Optical fibers are used for the transmission of optical signals. Optical fibers offer greatly increased transmission capability and transmission characteristics over traditional copper wires.
The use of optical fibers, however, does present some difficulties. Optical fibers are, in fact, conductors of light signals. To avoid losing or degrading the light signals being transmitted, there is a need for precise alignment and coupling any time optical fibers are connected to each other or to optical devices. Optic transfer efficiency is the term used to measure the ability of a connector to accurately couple the transmitted light signals.
As demands on communication media and data volume continue to increase, the advantages of using optical fiber bundles for transmission of signals across shorter distances, or for interconnecting local devices, continues to grow. With this growth has come a need to connect optical fibers accurately and economically to each other and to a multiplicity of devices.
Numerous optical cable connectors have been developed to aid in the connection of fiber optic cables. As data transmission requirements grow, single fiber connectors have given way to multiple fiber arrays, such as parallel ribbon cables, including a plurality of optical fibers.
Of considerable relevance to the problem of developing practical fiber optic connectors is the question of the optic transfer efficiency at the connector. Various factors affect the optic transfer efficiency at a connector. A key factor is axial misalignment, that is, when the connecting fiber ends are not aligned at the same linear axis. The ability to accurately align and retain fibers within a connector is an important component in obtaining and maintaining axial alignment.
Aligning the end face of a single fiber against another fiber, each having a thickness less than that of a human hair, presents formidable challenges. The problems multiply geometrically the more fibers are to be connected. As the number of fibers grow, it becomes increasingly difficult to maintain the transfer efficiency of each fiber connection in the connector. The need exists for articles and methods to improve alignment and retention characteristics of multi-fiber connectors.
The present invention relates to an article, an assembly and a method for accurately securing multiple optical fibers in a connector assembly. In particular, the present invention is directed to a novel ferrule and connector assembly that establishes fiber positions relative to grooved features for accurate alignment.
A ferrule in accordance with the present invention includes a ferrule base and a retaining element. The ferrule secures and optically aligns a plurality of optical fibers, each optical fiber having an outer surface. The fibers may be coated or uncoated. The ferrule base has alignment features, such as v-grooves, configured to receive and align the plurality of optical fibers. The retaining element covers at least a portion of the alignment features and secures the plurality of optical fibers against the alignment features. The retaining element has a contact surface that contacts the plurality of optical fibers, where the contact surface is able to conform to the outer surfaces of the plurality of optical fibers.
In exemplary embodiments, the retaining element has a hardness not greater than that of the alignment features of the ferrule block and/or not greater than that of the outer surfaces the plurality of optical fibers. The contact surface may overlap the whole or only a portion of the alignment features.
The retaining element may be a cover that mates with the base to form a ferrule or may be a pad that transmits pressure exerted by the cover or other members onto the fibers. The retaining element may include suitable materials such as Pellethane, Hytrel, or Santoprene. It also may include gels, fluid-filled bladders, or foam. In a particular embodiment, the retaining element may further include a curable adhesive to help retain the fibers and secure the ferrule.
In yet another embodiment, the retaining element may include a relatively rigid structural member and a compliant contact member, the contact member including the contact surface.
In one particular embodiment, the fibers are GGP coated fibers having about a 65 Shore-D hardness. The contact surface of the ferrule cover then has a durometer hardness equal or less than 65 Shore D.
Additional embodiments may be designed to receive multiple stacks of parallel optical arrays. The ferrule includes a base and a cover element, each having alignment features. Multiple optical fiber arrays may be stacked between the cover and the base interleaved with compliant pads.
A particular embodiment of a connector assembly for securing a plurality of optical fibers includes a base having a V-groove array that receives the plurality of optical fibers. A cover mates onto the base over at least a portion of the V-groove array and applies a retaining force upon the plurality of optical fibers. The cover has a compliant contact portion having a compression range that is equal to or greater than the expected fiber alignment height variability, wherein the compliant cover applies at least a portion of the retaining force to each one of the plurality of fibers.